Among the various video display systems available in the art, an optical projection system is known to be capable of providing high quality images in a large scale.
In FIG. 1, there is illustrated a prior art optical projection system 100 comprising a non-point light source 1, an optical baffle 2 provided with a plurality of reflective surfaces and corresponding number of slits, an array 3 of M.times.N actuated mirrors 4, a focussing, a projection and a collimating lenses 6,7,8, and a projection screen 9. Such an optical projection system is more fully described in a commonly assigned U.S. Pat. No. 5,379,081 entitled "Optical Baffling Device" and is incorporated by reference herein. In such a system, light emanating from the non-point light source 1 is focussed along a first optical light path 10 onto the reflective surfaces of the optical baffle 2 by the focussing lens 6. The reflective surfaces of the optical baffle 2 are in a facing relationship with the focussing lens 6 and the collimating lens 8. The light beam reflected from each of the reflective surfaces diverges along a second optical path 11 and quasi-collimated by the collimating lens 8, thereby being uniformly illuminated onto the array 3 of M.times.N actuated mirrors 4, each of the actuated mirrors 4 corresponding to each of the pixels to be displayed. The optical path of the reflected light from each of the actuated mirrors 4 is determined by the amount of deflection thereof. The reflected light beam from each of the undeflected actuated mirrors are focussed back to the optical baffle 2 by the collimating lens 8 along a second optical path 11 and stopped by the reflective surfaces thereof, whereas the reflected light beams from each of the deflected actuated mirrors are focused by the collimating lens 8 along a third optical path 12 so that a portion of the focused light beam passes though the slits thereof. The light beams from each of the actuated mirrors 4 which pass through the slits are transmitted to the projection lens 7 which focuses the transmitted light beam from each of the actuated mirrors 4 on the projection screen 9, thereby displaying each of the pixels corresponding thereto.
One of the major drawbacks of the above-described optical projection system is that it lacks means for providing the image in various sizes, and to an certain extent, the size of the overall system, which is predetermined, among others, by the focal length of the projection lens.